Year years 1960 41.63825658118905 1961 46.57701997035415 1962 53.28661057596427 1963 53.816421146948905 1964 54.50712280855001 1965 54.46905519512889 1966 55.544012765441096 1967 56.37008105399306 1968 56.78502331986799 1969 57.423578486481404 1970 58.03641151903439 1971 58.86068804893679 1972 59.41108408725592 1973 60.25748971554457 1974 60.858600882932784 1975 61.58067696501637 1976 62.34898637531413 1977 63.05720409910335 1978 63.644314427886954 1979 64.23028744275402 1980 64.71690168637014 1981 65.19942467254054 1982 65.66703814367024 1983 66.04540973409549 1984 66.43748293312666 1985 66.80390565583475 1986 67.15191774219993 1987 67.4970112362796 1988 67.74233687052407 1989 68.06317845183642 1990 68.27017914986446 1991 68.49225530273505 1992 68.95877060730251 1993 69.40109273938839 1994 69.6691898551765 1995 69.92265131344412 1996 70.20833401568557 1997 70.58369222272297 1998 70.97034433122982 1999 71.16578605643795 2000 71.55255395204976 2001 72.11293429067962 2002 72.45024172853023 2003 72.86440321910504 2004 72.96315999168091 2005 73.43933500839786 2006 73.79191692575036 2007 74.03501180913652 2008 74.00471203710285 2009 74.53250749517272 2010 74.73430067634618 2011 74.97132236656955 2012 75.22971722487904 2013 75.47911470932803 2014 75.73116269467954 2015 75.94873611561543 2016 76.13787495930362 2017 76.212440060682 2018 76.59395885035103 2019 76.79768228484083 2020 76.75970168802438 2021 76.39329501858417 2022 76.90204606245598